The present invention relates to an isolating method and a transferring method for semiconductor devices, and particularly to an isolating method and a transferring method for semiconductor devices which are suitable for application to the manufacture of miniaturized semiconductor devices.
In recent years, a variety of photoelectric devices using a semiconductor material have been developed and put to practical use, and among them are, for example, GaAs-based devices. In the case of forming, for example, a light-emitting diode (hereinafter referred to as LED) array using these GaAs-based devices as photoelectric devices, it is necessary to remove a GaAs substrate in order to provide optical access to the devices.
Here, the conventional method of forming an LED array by use of the GaAs-based devices as photoelectric devices will be described. First, as shown in FIG. 20, a laminate structure 102 for constituting, for example, AlGaInP-based LEDs is provided on a GaAs substrate 101. Specifically, as shown in FIG. 21, an n-type GaAs contact layer 103, an n-type AlGaInP clad layer 104, an AlGaInP active layer 105, a p-type AlGaInP clad layer, and a p-type GaAs contact layer 107 are sequentially grown on the GaAs substrate 101 by, for example, the metallo-organic chemical vapor deposition (MOCVD) method.
Next, as shown in FIG. 22, wet etching of the laminate structure 102 formed on the GaAs substrate 101 is conducted from the face side, i.e., from the side opposite to the side of the GaAs substrate 101, to thereby isolate LED devices. Specifically, first, selective etching of only the p-type GaAs contact layer 107 is conducted. Next, selective etching of AlGaInP, i.e., selective etching of the p-type AlGaInP clad layer 106, the AlGaInP active layer 105, and the n-type AlGaInP clad layer 104 is conducted. Subsequently, selective etching of the n-type GaAs contact layer 103 is conducted, to isolate the LED devices 108 as shown in FIG. 23.
Next, an adhesive layer 109 is provided on a transfer substrate 110, for example, a sapphire substrate or the like by use of an adhesive, and the GaAs substrate 101 is adhered to the transfer substrate 110 so that the adhesive layer 109 and the isolated LED devices 108 face each other as shown in FIG. 24. Then, as shown in FIG. 25, the GaAs substrate 101 is subjected to lapping and wet etching, to remove the GaAs substrate 101, thereby completing the transfer of the LED devices 108 onto the transfer substrate 110 and producing an LED array 111.
However, a thickness of generally about 100 μm of the GaAs substrate 101 is removed by the wet etching, and, therefore, the conventional method as above-mentioned has the problem that the period of time for which the LED devices 108 are exposed to the etching solution is prolonged due to unevenness of etching in plane. Namely, in the case of the conventional method, the portions where the etching has proceeded faster are exposed to the etching solution until the completion of the etching of the portions where the GaAs substrate 101 is difficultly removed due to slow progress of the etching. Therefore, the n-type contact layer 103 is partially etched, so that the LED devices 108 with a uniform surface condition are not formed, and, further, the etched condition is dispersed on the basis of each LED device 108, so that a uniform LED array 111 cannot be produced. Besides, as shown in FIG. 26, the etching solution for the GaAs substrate 101 consisting, for example, of a mixed solution of aqueous ammonia and an aqueous hydrogen peroxide solution would permeate through the interface between the LED devices 108 and the adhesive layer 109, resulting in damage to the AlGaInP active layer 105 and/or the p-type GaAs contact layer 107.
As a method of solving this problem, there has been proposed a method of providing an etching stop layer 112 consisting of AlGaInP between the GaAs substrate 101 and the n-type GaAs contact layer 103, as shown in FIG. 27. However, since the n-type GaAs contact layer 103 is a thin layer, in the case where the n-type GaAs contact layer 103 has defects or the like, there arises the problem that the etching solution permeates through the defects in the n-type GaAs contact layer 103 at the time of etching the p-type AlGaInP clad layer 106, the AlGaInP active layer 105 and the n-type AlGaInP clad layer 104, resulting in that the etching stop layer 112 consisting of AlGaInP would be etched. In this instance, at the time of etching the GaAs substrate 101 from the back side, the etching solution permeates to the device side through the etched portions of the etching stop layer 112, giving bad influences such as erosion of the device component portions.
In addition, in the case where the etching stop layer 112 consists, for example, of AlGaAs, there is the problem that it is difficult to obtain a clean and uniform surface upon etching of the GaAs substrate 101, due to the adhesion of reaction products onto the surface of the etching stop layer 112 after completion of the etching of the GaAs substrate 101, oxidation of AlGaAs, and the like phenomena. These problems become more conspicuous as the LED devices 108 are more miniaturized, which is one of the factors hampering the miniaturization of the LED devices 108.